Preventive Maintenance in Aviation

Aircraft are complex mechanical systems which involve complex assembly operations. To keep the aircraft fully operational and reliable, regular maintenance is required. Some maintenance techniques wait for a problem to occur to rectify it.

However, proactive maintenance techniques that keep aircraft in good condition and identify potential problems before they escalate are desired. This article analyzes one such proactive maintenance method; aircraft preventive maintenance.

What is preventive maintenance?

Preventive maintenance refers to various replacement tasks and preservation efforts that do not involve complex assembly operations. It comprises any work performed on the aircraft as part of a maintenance program without taking much apart.

Preventive maintenance includes a list of permitted tasks involving servicing aircraft parts or replacing small standard parts. Preventive maintenance is done on a regular schedule to prevent major problems from arising. 

Who performs preventive maintenance?

Preventive maintenance can be performed by two classes of people. The first class has certified technicians who have certification allowing them to perform preventive maintenance. The other class are holders of a pilot certificate. An aircraft owner or operator can only perform this type of maintenance if they are also a holder of a pilot certificate.

However, preventive maintenance cannot be done by pilots on aircraft used under CFR parts 121, 127,129, or 135. Also, pilots can only perform preventive maintenance if they have the necessary skills. Else, someone with a mechanic certificate issued under part 65.

Types of tasks on preventive maintenance

There are various maintenance tasks performed in preventive maintenance, and they vary depending on the aircraft, the preventive maintenance program approved for use by an organization, and the accessibility of the components. The preventive maintenance tasks are classified as follows:

• Preflight checks: done by pilots before flights. Pilots are required to perform these maintenance checks to ascertain that the aircraft is safe to fly.
• 50-hour and 100-hour inspections: 100-hour inspections are required by the Federal Aviation Administration (FAA) and are done after every 100 hours of flight. Although 50-hour inspections are not required by the FAA, it is sometimes viable to perform some inspections every 50 hours while performing an oil change. 
• Annual inspections: done annually and require rigorous inspections. It includes major inspections like aircraft engine inspections, weight and balance computations, logbook reviews, avionics and control checks, and parts checks.
• Progressive inspections: performed following the aircraft preventive maintenance program issued by the aircraft manufacturer according to the aircraft specifications. It is mostly utilized by high-use aircraft like those used by flight schools and fixed-based operators.

List of preventive maintenance activities

Under the various types discussed above, there are several specific aircraft preventive maintenance tasks performed. A full list of maintenance tasks that qualify as preventive aircraft maintenance tasks is captured in appendix 14 CFR Part 43.

Any tasks not mentioned in that list are not aircraft preventive maintenance tasks. Below is a summary of the list of inspection and maintenance tasks in preventive maintenance:

1. Replacing safety belts or inspection of the general condition of safety belts.
2. Inspecting the spark plug, setting the spark plug gap clearance, cleaning spark plugs, or replacing them.
3. Changing or repairing landing gear tires.
4. Replacing defective safety wiring.
5. Inspecting light wiring circuits and repairing broken circuits.
6. Making replacements to the hose connection except hydraulic hoses.
7. Lubrication of aircraft components that do not require disassembly.
8. Carrying out inspection and removal of magnetic chip detectors or replacing magnetic chip detectors.
9. Checking the hydraulic fluid level and replenishing as necessary.
10. Checking engine oil level and replenishing as necessary.
11. Refinishing decorative coating on the fuselage, excluding on balanced control surfaces.
12. Checking air filters, cleaning them, and replacing them when necessary to facilitate proper air flow.
13. Installing anti-misfuelling devices that reduce fuel tank filler openings.
14. Making simple fabric patches which do not require stitching ribs, removing control services or removing structural parts. For balloons, only repairs not requiring load tape repair as per the balloon type certificate data qualify as preventive maintenance.
15. Landing gear shock struts servicing.
16. Servicing landing gear wheel bearings or replacing the landing gear wheel bearings.
17. Making wheel and ski replacements where no weight and balance computation is necessary.
18. Applying preservative or protective material to all components that do not require the disassembly of any primary structure or operating system.
19. Making replacements of seat parts or approved aircraft cabin seats with replacement parts approved for the specific aircraft without disassembly of any primary structure or operating system.
20. Making cowling replacements that do not require disconnection of flight control systems or removal of engine propeller.

Difference with reactive repairs

Preventive aircraft maintenance differs from major repairs done on aircraft. The motivation to perform preventive maintenance stems from taking a proactive approach to preventing failure from occurring.

On the contrary, major repairs are performed to rectify a failure that has occurred. Preventive aircraft maintenance is done following a preventive maintenance program approved by the federal aviation administration. Unlike major repairs, it does not involve any major alterations on the aircraft.

Benefits of preventive maintenance program

Safety

Preventive aircraft maintenance improves safety in aviation. Aircraft preventive maintenance ensures that potential problems are captured and addressed before failure occurs during flight.

For instance, regular inspection and preventive maintenance tasks ensure that broken or deteriorating components are replaced with an approved unit before they can fail during flight.

Therefore, it promotes safety in aviation by preventing aircraft failure. Also, aircraft preventive maintenance improves the reliability of the aircraft. The maintenance tasks decrease the chances of equipment failure and in turn reduce aircraft downtime.

Prolonged lifespan of aircraft

Additionally, proactive maintenance improves the lifespan of aircraft components. So, preventive aircraft maintenance improves the reliability of aircraft and aircraft components.  

Closing the mechanical knowledge gap for pilots

The other benefit of preventive aircraft maintenance is improving the mechanic skills of pilots. A pilot who performs preventive maintenance becomes accustomed to the mechanics of an aircraft.

With the mechanical knowledge of their aircraft, pilots develop great skills in identifying issues before they occur. This, in turn, limits the need for performing major alterations to the aircraft because of equipment failure.

Compliance with regulations

Aircraft preventive maintenance increases compliance with regulations and promotes workplace safety. A preventive aircraft maintenance schedule ensures that technicians have ample time to perform maintenance tasks as opposed to trying to rush to perform major repairs which involve complex assembly operations after a breakdown.

Therefore, the technicians have a safe working environment, which complies with various workplace safety regulations.

Financial efficiency

Preventive aircraft maintenance improves efficiency. The maintenance program limits unplanned repairs, making operations more efficient. Lastly, aircraft preventive maintenance is cost-efficient. It increases the lifespan of components, reducing the costs incurred on major repairs.

What’s more, it allows owners to perform simple maintenance tasks, limiting costs on reactive repairs. So, aircraft preventive maintenance is beneficial, and all should adopt it as a valid way of maintaining aircraft.

Regulations governing preventive aircraft maintenance

Aircraft preventive maintenance is governed by regulations which everyone should follow while performing this type of maintenance. All procedures carried out during preventive maintenance should be logged systematically in a logbook.

Strict logs on dates and mechanics

The log details the description of the maintenance tasks done, the date when they are carried out, the signature of the person who performs the maintenance, and their certification number and type of certificate.

The signature counts as the approval for the aircraft to return to service after maintenance. Additionally, maintenance on a component requires a signature as a return to service approval.

Only certified personnel

Given the regulation, only personnel with certification are authorized to perform preventive maintenance. Examples of viable certifications include a mechanic certificate, a private pilot certificate issued by FAA, or a sport pilot certificate.

Only those with appropriate certification can issue a return to service through their signature on a maintenance log. An owner without certification can hire certified personnel or an organization with an operating certificate issued by the FAA as they have certified personnel to perform this type of maintenance. 

Logbooks should be task-appropriate

The maintenance logs should be made by personnel in the right logbook for each maintenance task. For instance, work done on the engine propeller should be logged in the engine logbook, propeller logbook, aircraft logbook, and the automatic flight control systems check in the avionics logbook.

However, work done on landing gear tires should be logged in the aircraft logbook. If you are unsure where to log maintenance tasks, you should enter a log on all the logbooks.

Repair stations and workplace safety

In cases where the FAA has issued an airworthiness directive requiring fixing a part for it to be an approved unit, such maintenance can be done while doing preventive maintenance. All workrooms where preventive aircraft maintenance is carried out should be kept clean, dry, and safe to work in.

On top of that, maintenance tasks should be performed in a station with the repair station certificate for the specific task. Standards of workplace safety must be met when performing aircraft preventive maintenance.

After completing all maintenance tasks prescribed in the certificate holder’s procedures, all placards and the appropriate certificates must be returned to their appropriate positions. The certificates include operating certificates, airworthiness certificate, and special airworthiness certificate.  

Schedule requirements

Worksite analysis

The success of a preventive aircraft maintenance program depends on the schedule adopted. A good schedule will meet specific requirements. The first requirement is adequate worksite analysis. A documented worksite analysis process promotes adherence to the set standards for workplace safety.

The worksite analysis details where components should be placed during maintenance, ensuring that proper written procedures consistent with FAA requirements are followed at all times.

Mandatory training

The other requirement is training. An approved training program is necessary to have a knowledgeable team that performs preventive maintenance well and adheres to the set regulations.

Everyone should use a special training program approved by the FAA to ensure excellent maintenance practices are adopted by the maintenance team. Not to add, training ensures that the maintenance team adapts to any changes in the aviation industry regarding preventive aircraft maintenance.

Hazard control

The last schedule consideration is a hazard prevention and control plan. Such a plan within the schedule ensures that any hazards during maintenance are mitigated.

Everybody in the repair facility should be trained and informed on hazardous situations, their control, and prevention. The staff should be acquainted or equipped with an appropriate risk management handbook.

Points to note

Preventive maintenance can be daunting to novices and inexperienced pilotes, but here are a few pointers to remember while performing aircraft preventive maintenance:

• You should have the approved manuals, tools, and parts before starting the maintenance process.
• You should follow the procedures detailed in the approved maintenance program.
• Only perform maintenance tasks that fall under preventive maintenance.
• Make logs of all the maintenance tasks you perform on the appropriate logbooks.
• Only certified personnel should perform preventive maintenance.

And never forget: don’t wait for a problem to appear to fix it. Chronic and overlooked problems are going to cost more time and resources than keeping your aircraft in overall good shape with preventive measures.